This application incorporates by reference Taiwanese application Serial No. 90100657, filed Jan. 11, 2001.
1. Field of the Invention
This invention relates to a driving method for a plasma display panel (hereinafter referred to as PDP) and a circuit thereof, particularly to a driving method for reducing a voltage difference of the sustaining electrode and circuit thereof.
2. Description of the Related Art
Please refer to FIG. 1, it shows a cross-sectional view of a conventional PDP structure. There are several sustaining electrodes X and scanning electrodes Y alternately disposed on the surface of the front glass substrate 102 and are parallel to each other. Each of the sustaining electrode X or scanning electrode Y comprises a transparent electrode 106 and an auxiliary electrode 108. The auxiliary electrode 108 is used to increase the conductivity of the transparent electrode 106. A dielectric layer 110 is positioned on the transparent electrode 106 and the auxiliary electrode 108, and a protective layer 112 covers the dielectric layer 110.
A plurality of address electrodes 114, which are perpendicular to the sustaining electrodes X and the scanning electrodes Y, are positioned on the surface of the rear glass substrate 104. Each address electrode 114 is formed below a fluorescent layer 116 and ribs (not shown in FIG. 1). The discharge space 118 is formed between the protective layer 112 and the fluorescent layer 116. The discharge space is filled with discharge gas, for instance, inert gases.
Referring to FIG. 2, it is the diagram of the electrode arrangement of the conventional PDP. The sustaining electrode X and the scanning electrode Y are alternately disposed, that is, these electrodes are arranged by the order of scanning electrode Y(1), sustaining electrode X(1), scanning electrode Y(2) and sustaining electrode X(2). The address electrodes A(1), A(2), A(3) and A(4) are perpendicular to the sustaining electrodes X and the scanning electrodes Y. Each discharge cell E1, can be turned on and off, is defined by the sustaining electrode X, scanning electrode Y and address electrode A.
Referring to FIG. 3, it is the diagram showing another electrode arrangement of the conventional PDP. The sustaining electrode X and the scanning electrode Y are arranged by the order of YXXY, that is, the electrodes are arranged by the order of the scanning electrode Y(1), sustaining electrode X(1), sustaining electrode X(2) and the scanning electrode Y(2). The address electrode A(1), A(2), A(3) and A(4) are perpendicular to the sustaining electrodes X and the scanning electrodes Y. Each discharge element E2, can be selectively turned on and off, is defined by each sustaining electrode X, scanning electrode Y and address electrode A.
Referring to FIG. 4, it is the diagram of the driving waveform for driving the conventional PDP in FIG. 2 or FIG. 3. In this driving method, there are three periods in each subfield, including a reset period P1, an address period P2, and a sustain period P3. The following description is the operation of a PDP having n sustaining electrodes X(1)xcx9cX(n), n scanning electrodes Y(1)xcx9cY(n) and m address electrodes A(1)xcx9cA(m).
To make sure that the data can be addressed correctly in the pixels, in the reset period P1, a priming pulse 402 of 340V is applied to the sustaining electrodes X(1)xcx9cX(n), and an erase pulse 404 with a positive voltage, a reset pulse 406 with a negative voltage and a stabilizing priming pulse 408 are sequentially applied to the scanning electrodes Y(1)xcx9cY(n). The wall charges of the discharge cells are reset to a certain energy state by the pulses described above. Those pulses also reduce the ionized charges in the discharge space 118.
During the address period P2, lots of scanning pulses 410 of xe2x88x92180V are inputted to the scanning electrodes Y(1)xcx9cY(n). A voltage V1, about 60V, is applied to the sustaining electrodes X(1)xcx9cX(n). According to the image data to be displayed, the address pulse 412 of 60V is selectively inputted to the address electrodes A(1)xcx9cA(m) for producing wall charges. Therefore, the wall charges can be increased in the selected discharge cells, and are used as the initial charges for a subsequent sustain period P3.
During the sustain period P3, the discharge cells emit UV light and the user will see visible light as UV photons hit the fluorescent layer 116. By the memory effect of the wall charges, the discharge cells are lighted after applying an alternating current with opposite polarities to the scanning electrodes Y(1)xcx9cY(n) and the sustain electrodes X(1)xcx9cX(n). The signals applied to the scanning electrodes Y(1)xcx9cY(n) and the sustain electrodes X(1)xcx9cX(n), are in a range between 180V and 0V, and these signals include a plurality of discharge sustaining pulse 414.
Please refer to FIG. 5 which is a block diagram of the circuit and used to drive the conventional PDP in FIG. 2 or FIG. 3. Take n=8 as an example. The Y driving circuit 502 includes a reset/scan circuit 504 and a Y sustaining circuit 506. The reset/scan circuit 504 should provide at lease one signal with a positive voltage and one signal with a negative voltage, so the reset/scan circuit 504 is a positive/negative polarity circuit. During the reset period P1 or the address period P2, the reset/scan circuit 504 provides signals with voltages of 180V, xe2x88x9290V or xe2x88x92180V to the scanning electrodes Y. During the sustain period P3, the sustaining circuit 506 provides signals with voltages of 180V or 0V to the scanning electrodes Y. During the address period P2 and the sustain period P3, the Y driving circuit 502 provides the signals to the multiplexer 508 and the scanning IC 510 which is electrically connected to all of the scanning electrodes Y(1)xcx9cY(8). The scanning IC 510 sequentially outputs the scanning pulse 410 to the scanning electrodes Y(1)xcx9cY(8) during the address period P2, and simultaneously provides discharge sustaining pulses 414 to the scanning electrode Y(1)xcx9cY(8) during the sustain period P3. Moreover, all of the sustaining electrodes X are coupled to the X driving circuit 514. The X driving circuit 514 includes a reset circuit 516 and a X sustaining circuit 512. The reset circuit 516 only provides signals with a positive voltage, so the reset circuit 516 is a positive polarity circuit.
Referring to FIG. 6, it shows the current IX of the sustaining electrode X, and the voltage of the sustaining electrode X and the scanning electrode Y during the sustain period P3 in FIG. 4. After the discharge sustaining pulse 414 is applied, the discharge cell is discharged, and a current Ids will pass through the sustaining electrode X, scanning electrode Y, X sustaining circuit 512 and Y sustaining circuit 506. The X sustaining circuit 512 and the Y sustaining circuit 506 include a lot of transistors, every transistor has its resistance, and the total resistance of these transistors is defined as Rds. When the current Ids is formed, a voltage difference V=Ids*Rds is occurred within a very short time because of the resistances Rds of these transistors. When the electric current flows out of one electrode, the voltage difference V is negative, and a notch may appear in the voltage waveform of the electrode. When the electric current flows in the electrode, the voltage difference V is positive, and a peak may appear in the voltage waveform of the electrode. In addition, whether a notch or a peak is formed may depend on the signals applied on these electrodes. When the sustaining electrode X is in a positive voltage (e.g. 180V) and the scanning electrode is in a relative negative voltage (e.g. 0V), the instant voltage difference V cause a voltage notch 602a in the voltage waveforms of the sustaining electrode X and a peak 602b in the voltage waveforms of the scanning electrode Y. The voltage difference V can be as higher as 60V. Therefore, the actual voltage waveforms of the sustaining electrode X and the scanning electrode Y are different from these of the inputted signals of the driving circuits. The voltage operation margin of the PDP is then reduced, and the electromagnetic radiation interference (EMI) becomes seriously when the notch or the peak is formed.
U.S. Pat. No. 6,072,449 discloses a method for driving the PDP and a method can reduce the instant voltage difference V. The voltage and the current waveforms for the sustaining electrode X and the scanning electrode Y are shown in FIG. 7. First, the scanning electrodes Y are divided to two groups including first scanning electrodes Y1 and second scanning electrodes Y2. Take a first scanning electrode Y1 and a second scanning electrode Y2 as the example, the discharge sustaining pulses with different phases are applied, respectively. Therefore, on the sustaining electrode X, the displacement current 702 caused by the voltage difference of the first scanning electrode Y1, the displacement current 702xe2x80x2 caused by the voltage difference of the sustaining electrode X, the discharge current 704 of the sustaining electrode X and the first scanning electrode Y1, the displacement current 706 caused by the voltage difference of the second scanning electrode Y2, and the discharge current 708 of the sustaining electrode X and the second scanning electrode Y2 will appear at different times. Therefore, the discharge currents 704, 708 become smaller. According to the above-mentioned equation V=Ids*Rds, the instant voltage difference can be reduced when the current is reduced. The voltage notches 710, 712 or peaks 714, 716 formed by the instant voltage difference V can also be reduced. However, the circuit is very complex, and thereby the cost is very high.
Referring to FIG. 8, it shows the block diagram of the driving circuit to produce the waveform in FIG. 7. The first scanning electrode Y1 and the second scanning circuit Y2 are respectively coupled to the scanning IC 810 and the scanning IC 820. There are many transistors in the Y driving circuit 802, so the scanning ICs 810, 820 can""t couple to only one Y driving circuit 802. Every scanning IC must couple to a corresponding Y driving circuit to output a different driving waveform. Therefore, the scanning ICs 810 and 820 are respectively coupled to the Y driving circuits 802 and 812 through the multiplexer 808 and 818. The Y driving circuit 802 includes a reset/scan circuit 804 and a Y sustaining circuit 806, and the Y driving circuit 812 includes a reset/scan circuit 814 and a Y sustaining circuit 816. The reset/scan circuits 804, 814 are negative/positive polarity reset circuits. A X driving circuit 826 includes a reset circuit 828 and a X sustaining circuit 824. Moreover, the Y driving circuits 802 and 812 respectively receive control signals C_Y(1) and the C_Y(2) from the phase shift controller 822 to produce different discharge sustaining pulses. The phase shift controller 822 further transmits one control signal C_X(1) to the X sustaining circuit 824 to maintain the synchronization of the sustaining circuit 806, 816 and 824. However, there are so many components in the above-mentioned circuit, the prior circuit would be very complicated and the manufacturing cost is high.
From the above description, the object of the present invention is to provide a driving method of a Plasma Display Panel (PDP)and circuit thereof. The driving method and circuit of the PDP reduces the voltage difference effectively and increases the operation margin. Especially, the driving method reduces the electromagnetic interference of the PDP efficiently. The object of the present invention is achieved with only a simple circuit.
According to the object of the present invention, a driving method of the PDP is disclosed. The PDP includes a first sustaining electrode, a second sustaining electrode, a scanning electrode and a data electrode. The scanning electrode is parallel to the first sustain electrode and the second sustain electrode. The data electrode is perpendicular to the first sustaining electrode. The driving method includes steps of: (a) providing an address period, (b) applying a scanning pulse to the scanning electrode during the address period and selectively applying a data pulse to the data electrode for writing in an image data, (c) providing a sustain period, and (d) applying a first pulse and a second pulse with different phases to the first sustaining electrode and the second sustaining electrode, and applying a third pulse to the scanning electrode for maintaining the image data. The first pulse and the second pulse produce a first discharge current and a second discharge current on the first sustaining electrode and the second sustaining electrode, and an time interval is formed between the second discharge current and the first discharge current to reduce an instant power consumption of the PDP.
According to another object of the present invention, a PDP driving circuit is also disclosed. The PDP includes a scanning electrode, a first sustaining electrode, a second sustaining electrode and a data electrode. The scanning electrode is parallel to the first sustain electrode and the second sustain electrode. The data electrode is perpendicular to the first sustaining electrode. The driving circuit of the PDP includes a Y driving circuit, a scanning IC, a first X sustaining circuit, a second X sustaining circuit and a phase shift controller. The scanning IC is coupled to the scanning electrode and the Y driving circuit. The first X sustaining circuit is coupled to the first sustaining electrode X1, and the second X sustaining circuit is coupled to the second sustaining electrode X2. The phase shift controller is coupled to the first X sustaining circuit and the second X sustaining circuit, the phase shift controller is commanded the first X sustaining circuit and the second X sustaining circuit to output a first and a second pulse, and the first and second pulse are in different phases.